What causes high low pressure & low high pressure?

[Stresst]

I brought my truck to an a/c-radiator shop to find out the condnser was plumbed backwards. Thinking this was the only issue I actually got excited that after 3 months this was good to go finally.

I received the replacement delphi compressor and brought it to the new shop, he installed it and same thing. After a few minutes it starting making noise like the other new one did and very high pressure.

What causes high low pressure & low high pressure on my 2000 Escalade with rear air. Low side is around 70 and high side is around 200lbs at idle?

This is totally effin obsurd how much time and money I wasted.

He told me the compressor is no good so I went to a local auto parts store to buy another compressor. ( 3rd one this week) I just called him being he closes at 3pm and I havent gotten a phone call and guess what same thing. pressures are way off.

Now he is swapping out the condenser (5th one I got / 3rd one thats going to be installed).

I must sound like a complete effen a-hole to everyone on TYF who has read my posts over the last 3 months.

I really dont know what to do!!!

 

[SunlitComet]

What causes high low pressure & low high pressure?


A bad compressor does. A noisy one just confirms it. Sorry man. How sure are you that there is no debris floating in there from a previous failure.

 

[Stresst]

I just went to pick the truck up, THE A/C IS FINALLY WORKING.....its the best its been for as long as I remember. I don't know how cold it blew before but its pretty darn good. At idle its about 54 on a digital and about 50 on a meat thermometer. On a short highway trip (less then 2 miles) it was down to 47 degrees and 44 on the meat therm.

It seems the rear expansion valve is no good. ( yes the one the other shop replaced on wednesday after they replaced it last month) He opened the system up again and installed the orifice in the condenser instead of the y-pipe. I don't know if there is a negative effect of doing this but for now its staying like that!

I called the other shop up and gave him a peace of my mind, between me screaming and his bad english I dont know if or what he understood but im going there monday with all my receipts.

Its amazing that he couldnt find the mistake, he is a very big shop. Brand new spray booth, 17 mechanics, fram machine, advertises on asian tv stations. But the shop whom fixed it was borderline butcher shop. Im not complaining by any means but you have to see this place. Some guy came in for a new radiator, he didnt have the correct size wrench to take his fan off so he used a 2' screwdriver/pry bar and a 5lb sledge, when he evacuated my system he hooked up a hose to the low side and the high side hose in a bucket of water. Heck when they charge systems they only use the low side. But yet they got my truck running! Amen!

 

[SunlitComet]

So give some details.

 

[Stresst]

So give some details.

Give some details? I gave TYC my life story over the last 3 months. There is actually a piece of tape on my shroud. It say's 2.75lbs, accum, orf,yellow dye, 04-20-11. What im getting at is this is the day he first did the work. This wednesday is the 3rd month anniversary of the first day I got bent over! Gonna add up all the receipts, it has to be near 3k. I am so happy its working im not even mad about the money. (well at least until the CC bills come rolling in).

 

[SunlitComet]

the "give some details" post was before you edited post #3 when all you said it was working and edited 17 minutes later with more details.

, literally, in the truck.

---------- Post added at 04:43 PM ---------- Previous post was at 04:40 PM ----------

BTW, while the evacuation into a bucket of water is a definite no-no, you never ever charge a system using the high pressure port. Only the low one.

 

[Stresst]

the "give some details" post was before you edited post #3 when all you said it was working and edited 17 minutes later with more details.

, literally, in the truck.

---------- Post added at 04:43 PM ---------- Previous post was at 04:40 PM ----------

BTW, while the evacuation into a bucket of water is a definite no-no, you never ever charge a system using the high pressure port. Only the low one.

I always seen both hoses hooked up, I assumed they charged it with both sides but I maybe wrong. These guys only used the low side while checking car and truck's and when I say trucks I mean tractor trailer's and roll off's. They add a little freon at a time. Wait 5-10 mins and feel the hoses, condenser, accum before adding more. Then the process starts over again. No high side guage. Hhe used it on my truck but not once did I see any of the techs there using it. He said "he can see everything from one guage, if you know what your doing you dont need it".

---------- Post added at 07:57 PM ---------- Previous post was at 07:48 PM ----------

I do want to thank everyone for your help. It was someone in one of the threads that brought many things to my attention which aided in solving the problem. One was someone mentioned about differant btu ratings of condensers. When Pep boys installed the fan I mentioned something to the tech and then he confirmed something didnt look rite. Wound up that the wrong condenser was supplied by the shop who did the work. It was a condenser for a pickup/tahoe w/o rear air. The second thing was the the compressor being plumbed incorrectly. I mentioned it to the guy today and he asked wanna check it? So I actually took the grill/fascia off and sure enough. He probabaly would have found it eventually but I brough it to his attention. Thank you all!

---------- Post added at 08:01 PM ---------- Previous post was at 07:57 PM ----------

I do have two concerns one is the rear expansion, is this bad running the orifice in the condenser? Should I have the rear expansion replaced? The other thing is the TYC condenser I just bought. He said they are crap that they dont dissapate heat like there supposed to. Maybe this is why im idling around approx 55 degrees?? I can return it now and get my money back within 30 days. Or do I leave well enough alone? It was down to 87 degrees outside when I picked the truck up so we will see how it goes in the next few day's nevermind they are talking about a humid heat wave next week. I will make up my mind then, rite now gonna enjoy it for what it is.

 

[SunlitComet]

any number of hoses can bee used just as long as certain procedures are done in specific ways. You can have high/low connected and active on their gauges as long during charging freon into the system goes thru the low side only even though the high gauge is monitoring the pressure in the system. Evacuation is best with vacuum on both sides after the recovery of the system. Recovery is the same but a proper recovery machine(not a bucket of water which is still illegal and stupid) determines through built in electronics which line opens when under certain critera as the machine wants to get it out as quickly and safely as possible while trying to maintain the compistion of freon as it enters the recovery tank but not digest liquid directly into it pumping mechnism. It is complicated to explain all the details here but I could recommend a huge book that would explain it all(May get flashback so maybe not a good idea).

As far as rear valve a malfunctioning valve will ruin efficiency and not work correctly. and the orifice in front should be the in the y pipe where the design put it. It is only for the front evaporators use not both. That is why the rear has its own expansion valve. The rear evaporator is to far away from the rest of front system to be work effectively without it.

If you system works really well with the condenser you have leave it unless it is proven is to be faulty. As long as dimensions of core, piping and fitting are correct and the cooling finnage looks good just leave it.

 

[Stresst]

Thanks for the reply. I will see how the next few's day's go as were in store for a heat wave. As long as the temp is comfortable I will leave it.

Please briefly explain what you mean by its too far from the rear evap to work properly.

 

[SunlitComet]

you want the expansion of freon to happen just before entering the evap not 15 or so feet away from it. if the rear evap had it expansion valve all the way in front. the line between it and the rear evap would absorb all the outdoor heat and the rear evap would not work properly. When you put the it on the rear evap everything upstream is pressurized and hot. As soon as it goes thru the expansion valve pressure reduce freon get cold and the evap absorbs the surrounding heat. hence it gets cold and the blower blows air thru it to lower the temperature of the air.

Want a tech book recommendation just in case?